People have commonly used wood fires for warmth, but also for adding to the ambiance of their environment at the same time. Wood fires typically give off yellow and orange colors. Various methods have been employed to enhance the coloration of such decorative fires. One method known for many decades is presoaking firewood in a metallic salt solution, and then drying before burning. Brockbank in U.S. Pat. No. 4,062,655 discloses how to make synthetic fire logs impregnated and coated with color-enhancing chemicals.
In another prior art patent example, Bramhall et al in U.S. Pat. No. 2,622,017 teach a fire kindling device that includes a cup containing color-producing salts encased in wax. The preferred chemicals are cupric chloride, strontium chloride, and potassium nitrate, with the potassium nitrate making up less than half by weight to avoid pyrotechnical effects. Similarly, Young in U.S. Pat. No. 2,398,571 discloses additional chemical agents which can be added to slow burning fuel for prolonged coloration.
Oberhardt in U.S. Pat. No. 4,309,189 teaches chemical compound mixtures and methods for producing prolonged coloring of fires. Chloride salts of copper, strontium, potassium, and barium are prominent in Oberhardt's examples. Also taught are methods of containing the chemical powders, such as in packets or bound with wax-like binding agents.
Davis is U.S. Pat. No. 6,203,586 discloses a fire color enhancement system which teaches placing a section of garden hose inside a copper tube which has melting end caps to prevent escape of the garden hose before placement in the fire. Davis mentions plastic and rubber hoses, but says nothing about the need for any chlorine compounds or holes along the copper tube.